Some printing apparatuses are configured to print an image of a dot pattern on a printing medium such as paper or a thin plastic plate on the basis of image information. Of these printing apparatuses, an inkjet printing apparatus discharges ink (printing solution) as a printing agent from the discharge apertures of a printhead, and attaches the ink to the printing medium to print.
In the inkjet printing apparatus which treats liquid ink as a printing agent, ink evaporates if the connecting portion between the ink tank and the printhead is not properly sealed. In a state (demounting state) in which an ink tank which has been mounted on the printhead is demounted from the printhead, ink evaporation from the connecting portion tends to proceed, and ink may stick within the ink flow path. If the demounting state of the ink tank continues for a long time, bubbles may enter the ink flow path in the printhead. Ink evaporation and entry of bubbles become more serious as the ink tank demounting time becomes longer.
If the ink flow path is not filled with ink owing to ink evaporation and entry of bubbles, bubbles flow into nozzles serving as ink discharge portions of the printhead, and the printhead fails to discharge ink (non-discharge state). Since no sufficient amount of ink flows in the above case, the size of ink droplets becomes smaller than that when the ink flow path is normally filled with ink. As a result, ink droplets may land at points different from desired landing points on a printing medium, or no fine dot shape can be obtained on a printing medium. Further, once sticking occurs in the ink flow path upon ink evaporation, the ink flow is obstructed at the portion of fixation, and ink supply becomes late. In the worst case, ink clogs nozzles or flow paths.
In this manner, degradation of the image quality or a failure in printing itself may occur due to mounting/demounting of the ink tank.
In order to solve these problems, a conventional printing apparatus generally executes a recovery operation upon newly mounting an ink tank. The recovery operation is performed to remove bubbles from the ink flow path, wipe clogging, and remove paper dust and another dust. More specifically, the recovery operation executes a sucking operation to suck ink from a nozzle while tightly closing the nozzle (discharge aperture) portion of the printhead with a cap, a preliminary discharge operation to discharge ink irrespective of printing, or a wiping operation to clean the nozzle surface of the printhead. These operations are combined in accordance with conditions to control the printing apparatus so as to keep the printhead optimal.
If, however, a sufficient recovery operation is executed every time when the ink tank is mounted, an ink amount consumed by the recovery operation increases, and the running cost increases.
In order to solve these problems, according to Japanese Patent Laid-Open No. 2000-127448, the demounting time period of an ink tank is detected, and an ink amount to be sucked by a recovery operation is set on the basis of the demounting time period. More specifically, as the demounting time period of the ink tank is longer, the ink suction amount is set larger.